Using C# to measure the width of a string in pixels in a cross platform way

I have some existing C# code that uses System.Drawing.Common to measure the approximate width of a string in pixels:

var text = "abc123 this is some long text my dog's name is fido.";

using (var bitmap = new Bitmap(500, 50))
using (var graphics = Graphics.FromImage(bitmap))
{
    // Size: 9 Points
    using var font = new System.Drawing.Font(familyName: "Times New Roman", emSize: 9f);
    
    var ms = graphics.MeasureString(text, font);
    
    // Output: 'abc123 this is some long text my dog's name is fido.' via System.Drawing: 394.00195 x 22.183594
    Console.WriteLine($"'{text}' via System.Drawing: {ms.Width} x {ms.Height}");
}

After upgrading to .NET 6.0, I got a bunch of warning messages telling me that these graphics primitives are only supported on Windows. I want this measurement to work on other platforms, so I tried to do something similar with both SkiaSharp:

var text = "abc123 this is some long text my dog's name is fido.";

using (var paint = new SKPaint())
{
    paint.Typeface = SKTypeface.FromFamilyName("Times New Roman");
    
    // Size: 12px
    paint.TextSize = 12f;
    
    var skBounds = SKRect.Empty;
    var textWidth = paint.MeasureText(text.AsSpan(), ref skBounds);
    
    // Output: 'abc123 this is some long text my dog's name is fido.' via SkiaSharp: 251.13867 x 12
    Console.WriteLine($"'{text}' via SkiaSharp: {skBounds.Width} x {skBounds.Height}");
}

And ImageSharp:

var text = "abc123 this is some long text my dog's name is fido.";

// Size: 12px
var imgSharpFont = SixLabors.Fonts.SystemFonts.CreateFont("Times New Roman", 12f);
var imgSharpMeasurement = TextMeasurer.Measure(text, new RendererOptions(imgSharpFont));

// Output: 'abc123 this is some long text my dog's name is fido.' via ImageSharp: 251.13869 x 14.589844
Console.WriteLine($"'{text}' via ImageSharp: {imgSharpMeasurement.Width} x {imgSharpMeasurement.Height}");

However, as you can see, I can't get SkiaSharp or ImageSharp to produce the same width, although they produce similar results:

'abc123 this is some long text my dog's name is fido.' via System.Drawing: 394.00195
'abc123 this is some long text my dog's name is fido.' via SkiaSharp: 251.13867
'abc123 this is some long text my dog's name is fido.' via ImageSharp: 251.13869

I don't understand graphics programming enough to know what I'm missing. It might be a unit conversion between Points and Pixels, or perhaps I'm not setting the correct properties. Any ideas on how to make SkiaSharp and/or ImageSharp return the same width measurement as System.Drawing.Common?

Thank you.

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